Streptomyces strain applied as tomato seed coatings to improve plant performance

Streptomyces showed a remarkable ability to modulate plant response and colonize plant tissues as endophytes. As soil inhabitants they are also good rhizosphere colonizers and play a crucial role in the plant microbiome shaping and making them good candidates as microbial biostimulants. A Streptomyces spp. strain (DEF17) was tested on tomato plants grown under water deficit to assess its effectiveness in modulating plant growth by seed coating application. Seed colonization tests confirmed the ability of this strain to colonize the emerging root of plant after seed treatment. Preliminary studies on the growth-induced effect of DEF17 treated plants showed an increased height of tomato plants at three weeks post seeding indicating its ability in modulating the plant growth. The aim of the experiment was to evaluate the effect of this Streptomyces strain in tomato plants grown under water shortage. The focus has been laid on physiological parameters, stress indices, and quality of the production. Interestingly, the presence of DEF17 induced different effects on tomato plants, affecting the concentration of chlorophylls and carotenoids, carbohydrates, and nitrates. At the same time the application of the strain induced a significant decrease in proline concentration in tomato leaves grown under non-stressful condition. Further studies on the production of metabolites and mechanisms of action of DEF17 strain are warranted to deepen its activities and potential use ad biostimulant product in agriculture.